Nanoparticle compositions and methods of making and using the same

ABSTRACT

Water soluble graphene oxide nanoparticles (GO) are provided having graphene sheets containing carboxylic and hydroxyl groups. The diameter of the GO when present in a closed form range from about 40 nm to 120 nm. Eco-friendly methods are provided for producing the GO. Methods for reversible encapsulation of a molecule within water soluble carbon nanoparticles (wsCNP) including the GO nanoparticles are provided that allow for delivery of the wsCNP loaded with therapeutic and/or imaging agents to a subject in need by releasing the therapeutic/imaging agent upon an increase in pH above about 7.2. The wsCNP have been shown to cross the blood brain barrier in a mouse model of vascular dementia, and methods are provided for delivering the wsCNP loaded with a therapeutic and/or imaging molecule to the brain.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/278,232, filed Sep. 28, 2016, which claims the benefit of priorityfrom U.S. Provisional Patent Application Nos. 62/234,294 and 62/234,252,both filed Sep. 29, 2015, each of which are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The presently disclosed subject matter relates to nanoparticlecompositions and methods of making and using the disclosed compositions.

BACKGROUND

Synthesis of graphene oxide (GO) from graphite is dominated by theclassic method introduced by Hummers [1], which comprises variousoxidizing agents in corrosive oxidizing acid mixtures [2, 3]. In arecent study, GO has been produced from anthracite coal by treating withconcentrated nitric acid in the absence of oxidizing salt mixtures toachieve quantum graphene oxide [4]. The disclosed prior art methodsproduce graphene 20 oxide by oxidative treatment of carbon. Further, thesize of GO produced using prior art methods lies in two extremes (i.e.,micrometer-sized particles when produced from graphite and less than 20nm in size when produced from anthracite coal).

Nanoparticle-based compositions have been developed as vehicles forparenteral delivery of genes, proteins, and drugs that enter the brainby nasal insufflations (International patent Application Publication No.WO 2013/040295). Particularly, the nanoparticles target the divalentmetal transporter expressed on olfactory nerve terminals to transportdivalent cation-coated or cation-containing nanoparticles to all regionsof the brain. However, these nanoparticles suffer from the limitation ofrequiring pegylation for solubility.

Pericyte cells in a healthy brain play a crucial role in thefunctionality of the selective permeable space between the bloodcirculatory system and central nervous system (i.e., the blood-brainbarrier (“BBB”)). The BBB regulates brain homeostasis and includessealed endothelial cells that line the blood vessels that selectivelypermit the entry of necessary molecules to pass into the brain throughtight junctions and enzymatic carriers. The BBB is the greatestimpediment preventing the use of diagnostic or therapeutic probes to becarried out by blood in combating neuronal disorders and/or to arrestthe growth of tumors inside the brain. Particularly, pericyte cellscreate tight junctions that protect vesicle trafficking through theendothelial cells and inhibit the effects of CNS immune cells. Inaddition, pericytes act as contractile cells that assist in controllingand/or regulating flow within blood vessels and/or between blood vesselsand the brain.

Moreover, the elasticity of pericyte cells allows expansion to reduceinflammation, thus allowing harmful substances to be diffused out of thebrain. Pericyte dysfunction is associated with neurodegenerativediseases. Accordingly, pericytes are an important component of theneurovascular unit that contributes to the integrity of the BBB. CADASIL(Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts andLeukoencephalopathy) is one of the most common small vessel diseases andis a major contributor of vascular dementia in humans.

Primarily, CADASIL is believed to be caused by the Notch3 mutation.Recently, ultra-structural changes in pericytes have been shown inCADASIL. A murine model of CADASIL (R169C; Tg88 by overexpression ofmutated transgene) is now available.

Thus, it would be beneficial to provide nanoparticle compositions ofintermediate size, and methods of producing the nanoparticles. Further,it would be beneficial to provide non-toxic compositions capable ofdelivering therapeutic and imaging agents across the BBB.

SUMMARY

In some embodiments, the presently disclosed subject matter is directedto a method for making graphene oxide nanoparticles, the methodcomprising: (a) treating a material comprising one or a combination ofwood charcoal, low grade coal, or carbonized plant biomass in a dilutealkali solution; and (b) separating the solution from the insolublematerial and neutralizing the solution, wherein a precipitate thatappears after neutralization of the solution comprises graphene oxidenanoparticles having a plurality of sheets ranging in size from about 40nm to 200 nm in the open form. In some embodiments, the method furthercomprises washing the precipitate with cold water. In some embodiments,the method comprises one or more of the following: the dilute alkalisolution is 10% sodium hydroxide solution; the treating in dilute alkalisolution is performed at a temperature ranging from about 25° C. to 40°C. (such as about 40° C.); the treating with dilute alkali solution isperformed until the solution turns a yellow-brown color; the woodcharcoal, low grade coal or carbonized biomass is in a powdered form;wherein the wood charcoal, low grade coal or carbonized biomass isessentially free of aromatic hydrocarbons and other associated solubleorganic compounds; and/or the mineral acid is hydrochloric acid.

In some embodiments, the presently disclosed subject matter is directedto a material comprising graphene oxide nanoparticles, the materialproduced by a process comprising: (a) treating a material comprising oneor a combination of wood charcoal, low grade coal, or carbonized plantbiomass in a dilute alkali solution; and (b) separating the solutionfrom the insoluble material and neutralizing the solution, wherein aprecipitate that appears after neutralization of the solution comprisesgraphene oxide nanoparticles having a plurality of sheets ranging insize from about 40 nm to 200 nm in the open form.

In some embodiments, the presently disclosed subject matter is directedto a material comprising graphene oxide nanoparticles (GO), wherein theGO comprises a plurality of graphene sheets, wherein a majority of thegraphene sheets have a diameter when present in a closed form rangingfrom about 40 nm to 120 nm, and wherein the graphene sheets have aplurality of carboxylic and hydroxyl groups on the plurality of sheets.In some embodiments, the carboxylic groups comprise at least about 20%of the total weight of the GO; wherein the GO has a solubility inaqueous solution at a concentration of about 1 mg GO/mL; the GO displaysfluorescence in the blue, green, red, and infra-red spectra; and/or theGO has amphiphilic properties.

In some embodiments, the presently disclosed subject matter is directedto a method for making graphene oxide nanoparticles, the methodconsisting essentially of treating a material comprising one or acombination of wood charcoal, low grade coal, or carbonized plantbiomass in an alkali solution, wherein a precipitate that appears afterneutralization of the solution comprises graphene oxide nanoparticleshaving a plurality of sheets ranging in size from about 40 nm to 200 nmin the open form. In some embodiments, the method further compriseswashing the precipitate with cold water. In some embodiments, the methodcomprises one or more of the following: the alkali solution is 10%sodium hydroxide solution; the treating in alkali solution is performedat a temperature ranging from about 250° C. to 40° C. (such as about 40°C.); the treating with alkali solution is performed until the solutionturns a yellow-brown color; the wood charcoal, low grade coal orcarbonized biomass is in a powdered form; the wood charcoal, low gradecoal or carbonized biomass is essentially free of aromatic hydrocarbonsand other associated soluble organic compounds; and/or theneutralization is performed with hydrochloric acid.

In some embodiments, the presently disclosed subject matter is directedto a material comprising graphene oxide nanoparticles, the materialproduced by a process consisting essentially of treating a materialcomprising one or a combination of wood charcoal, low grade coal, orcarbonized plant biomass in an alkali solution, wherein a precipitatethat appears after neutralization of the solution comprises grapheneoxide nanoparticles having a plurality of sheets ranging in size fromabout 40 nm to 200 nm in the open form.

In some embodiments, the presently disclosed subject matter is directedto a method for reversible encapsulation of a molecule within a watersoluble carbon nanoparticle (wsCNP), the method comprising: contacting awsCNP in an open form with a molecule to be encapsulated within thewsCNP in a solution, wherein the wsCNP has a plurality of graphenesheets comprising a plurality of carboxylic and hydroxyl groups on thegraphene sheets, wherein the wsCNP has a closed form at a subsequenttime and the encapsulated molecule can be released from the closed formwsCNP upon exposure of the wsCNP to a pH of about 7.2 or greater. Insome embodiments, the method comprises one or more of the following: amajority of the graphene sheets when present in the closed form have adiameter ranging from about 2 nm to 120 nm; a majority of the graphenesheets when present in the closed form have a diameter ranging fromabout 40 nm to 120 nm; and/or the wsCNP is produced by a processcomprising: (a) treating a material comprising one or a combination ofwood charcoal, low grade coal, or carbonized plant biomass in a dilutealkali solution; and (b) separating the solution from the insolublematerial and neutralizing the solution, wherein a precipitate thatappears after neutralization of the solution comprises graphene oxidenanoparticles having a plurality of sheets ranging in size from about 40nm to 200 nm in the open form.

In some embodiments, the presently disclosed subject matter is directedto a water soluble carbon nanoparticle (wsCNP) having a moleculeencapsulated therein, the wsCNP comprising: a plurality of graphenesheets in a closed form at a pH of about 6.8 or less, wherein a moleculeis encapsulated within the closed wsCNP, wherein a plurality ofcarboxylic and hydroxyl groups are present on the plurality of sheets,and wherein the molecule can be released from the closed form wsCNP at apH of about 7.2 and higher. In some embodiments, a majority of theclosed wsCNP have a diameter ranging from about 2 nm to 120 nm and/or amajority of the closed wsCNP have a diameter ranging from about 40 nm to120 nm. In some embodiments, the wsCNP is produced by a processcomprising: (a) treating a material comprising one or a combination ofwood charcoal, low grade coal, or carbonized plant biomass in a dilutealkali solution; and (b) separating the solution from the insolublematerial and neutralizing the solution, wherein a precipitate thatappears after neutralization of the solution comprises graphene oxidenanoparticles having a plurality of sheets ranging in size from about 40nm to 200 nm in the open form. In some embodiments, the molecule is animaging agent; the molecule is a therapeutic agent; the molecule is atherapeutic agent for treatment of a brain disorder; the molecule is oneor a combination of Donepezil, TPP, a protein, a peptide, a smallmolecule, a nucleic acid, a single strand DNA, a double strand DNA, anRNA, an siRNA, an oligonucleotide, a gene, a gene fragment, an imagingagent, or a lanthanide; and/or the molecule is a therapeutic agent fortreatment of cancer. In some embodiments, the wsCNP further comprisesone or more biomolecules or divalent metals to target delivery of thewsCNP with the encapsulated molecule to a cell, tissue, brain, or organ.In some embodiments, the biomolecule is a protein, a receptor, anaptamer, a ligand, or an antibody. In some embodiments, the divalentmetal is manganese.

In some embodiments, the presently disclosed subject matter is directedto a method of delivering a molecule to a subject by delivering to thesubject a composition comprising a water soluble carbon nanoparticle(wsCNP) having the molecule encapsulated therein, wherein theencapsulated molecule is released from the wsCNP into the subject as aresult of the increase in pH after delivery to the subject's body. Insome embodiments, the method comprises one or more of the following:delivering to the subject comprises intravenous injection of the subjectwith the composition comprising the wsCNP; delivering to the subjectcomprises inhalation of the composition comprising the wsCNP; themolecule is an imaging agent; the molecule is a therapeutic agent fortreatment of a brain disorder; the brain disorder comprises dementia,vascular dementia, or Alzheimer's; the molecule is one or a combinationof Donepezil, TPP, a protein, a peptide, a small molecule, a nucleicacid, a single strand DNA, a double strand DNA, an RNA, an siRNA, anoligonucleotide, a gene, a gene fragment, an imaging agent, or alanthanide; the molecule is a therapeutic agent for treatment of cancer;and/or the molecule is for delivery in a subject across the blood brainbarrier (BBB). In some embodiments, the wsCNP further comprises one ormore biomolecules or divalent metals to target delivery of the wsCNPwith the encapsulated molecule to a cell, tissue, brain, or organ of thesubject. In some embodiments, the biomolecule is a protein, a receptor,an aptamer, a ligand, or an antibody. In some embodiments, the divalentmetal is manganese.

BRIEF DESCRIPTION OF THE DRAWINGS

The previous summary and the following detailed descriptions are to beread in view of the drawings, which illustrate some (but not all)embodiments of the presently disclosed subject matter.

FIG. 1A is a bar graph illustrating the size distribution of grapheneoxide by dynamic light scattering (DLS) in accordance with someembodiments of the presently disclosed subject matter.

FIG. 1B is a graph of absorbance versus wavelength showing electronicspectra of graphene oxide (solid line for fresh, dotted line for aged orthermally treated) in accordance with some embodiments of the presentlydisclosed subject matter.

FIG. 10 is a graph of absorbance versus wavelength showing electronicspectra of graphene oxide in PBS buffer (solid line is pH 6.8 PBSbuffer; dotted line is pH 7.4 PBS buffer) in accordance with someembodiments of the presently disclosed subject matter.

FIG. 2A is an atomic force microscopy (AFM) image of open fistedgraphene oxide in accordance with some embodiments of the presentlydisclosed subject matter.

FIG. 2B is an AFM image of aged closed fisted graphene oxide inaccordance with some embodiments of the presently disclosed subjectmatter.

FIG. 2C is a scanning electronic microscopy (SEM) image of grapheneoxide open fished from on exposure with ammonia vapor in accordance withsome embodiments of the presently disclosed subject matter.

FIG. 2D is an SEM image of close fisted graphene oxide in accordancewith some embodiments of the presently disclosed subject matter.

FIG. 2E is a high resolution transmission electron microscopy (HRTEM)image of open fisted graphene oxide in accordance with some embodimentsof the presently disclosed subject matter.

FIG. 2F is an HRTEM image of close fisted graphene oxide in accordancewith some embodiments of the presently disclosed subject matter.

FIG. 3A is a Fourier Transform Infrared Spectroscopy (FT-IR) spectra ofopen fisted graphene oxide after treatment in NH₄OH—H₂O and drying undervacuum at −37° C. in accordance with some embodiments of the presentlydisclosed subject matter.

FIG. 3B is a FTIR spectra for graphene oxide treated with dilutehydrochloric acid and evaporated under vacuum in accordance with someembodiments of the presently disclosed subject matter.

FIG. 3C is a FTIR spectra for graphene oxide treated with NID₄OD—D₂O anddried under vacuum at −37° C. in accordance with some embodiments of thepresently disclosed subject matter.

FIGS. 4A and 4B are bar graphs illustrating the size distribution fromAFM image analysis of graphene oxide nanoparticles produced according tosome embodiments of the presently disclosed subject matter in the openfirst structure (FIG. 4A) and in the closed fist, spherical structure(FIG. 4B).

FIG. 5A is an HRTEM image of graphene oxide-TTP after treatment withNH₃, showing the graphene oxide in the open form in accordance with someembodiments of the presently disclosed subject matter.

FIG. 5B is an HRTEM image of graphene oxide-TPP, showing the grapheneoxide in the closed form (inset: enlarged section showing the presenceof stacked TPP within the graphene oxide) in accordance with someembodiments of the presently disclosed subject matter.

FIG. 5C is an SEM image of graphene oxide-TPP after treatment with NH₃,showing the graphene oxide in the open form in accordance with someembodiments of the presently disclosed subject matter.

FIG. 5D is an SEM image of graphene oxide-TPP, showing the grapheneoxide in the closed form in accordance with some embodiments of thepresently disclosed subject matter.

FIG. 5E is an electronic spectra of graphene oxide-TPP in PBS buffer, pH7.4, showing the open form of the graphene oxide (inset: electronicspectrum of dichloromethane extract) in accordance with some embodimentsof the presently disclosed subject matter.

FIG. 5F is an electronic spectra of the graphene oxide-TPP in PBSbuffer, pH 6.8, showing features of the encapsulated TPP within theclosed form in accordance with some embodiments of the presentlydisclosed subject matter.

FIG. 5G is an electronic spectra of graphene oxide-donepezil in PBSbuffer, pH7.4, showing the open form of graphene oxide (inset:electronic spectrum of dichloromethane extract showing the features ofdonepezil) in accordance with some embodiments of the presentlydisclosed subject matter.

FIG. 5H is an electronic spectra of graphene oxide-donepezil in PBSbuffer, pH 6.8, which shows features of the encapsulated donepezilwithin the closed form of the graphene oxide in accordance with someembodiments of the presently disclosed subject matter.

FIG. 6A is a powder X-ray diffraction (XRD) spectra of graphene oxideaccording to one or more embodiments of the presently disclosed subjectmatter.

FIG. 6B is an XRD spectrum of graphene oxide-TPP in accordance with someembodiments of the presently disclosed subject matter.

FIG. 6C is an enlarged view of the spectrum from FIG. 6B, illustratingthe presence of both the broad peaks from the graphene oxide and thesharp peaks from the TPP.

FIG. 7A is an SEM image of freshly prepared water soluble quantum carbondots (wsCdot) according to some embodiments of the presently disclosedsubject matter.

FIG. 7B is an SEM image of freshly prepared wsCdot after exposure to NH3vapour in accordance with some embodiments of the presently disclosedsubject matter.

FIG. 7C is an electronic spectrum of wsCdot-donepezil composite in PBS,pH 6.8, where extraction with DCM did not remove the donepezil from thecomposite in accordance with some embodiments of the presently disclosedsubject matter.

FIG. 7D is an electronic spectrum of wsCdot-donepezil composite in PBS,pH 7.4 in accordance with some embodiments of the presently disclosedsubject matter, where extraction with DCM revealed a signature donepezilspectrum that is shown in the inset.

FIG. 8A is an electronic spectra of DNA alone showing a peak at 259 nmin accordance with some embodiments of the presently disclosed subjectmatter.

FIG. 8B is an electronic spectra of graphene oxide alone in accordancewith some embodiments of the presently disclosed subject matter.

FIG. 8C is an electronic spectra of graphene oxide-DNA composite showingthe characteristic absorption peak of DNA at 259 nm and also showing thebackground absorption of the graphene oxide in accordance with someembodiments of the presently disclosed subject matter.

FIG. 9 is a microscopic image of a mouse brain in which the wsCNP hascrossed the BBB into the brain according to one or more embodiments ofthe presently disclosed subject matter.

FIG. 10A shows electronic spectra of untreated graphene oxide in ethanolin accordance with some embodiments of the presently disclosed subjectmatter.

FIG. 10B shows electronic spectra of Mn(acac)₃ in ethanol in accordancewith some embodiments of the presently disclosed subject matter.

FIG. 100 shows electronic spectra of graphene oxide containing Mn(acac)₃in accordance with some embodiments of the presently disclosed subjectmatter.

FIG. 10D shows simulated spectra of combined graphene oxide andMn(acac)₃ in accordance with some embodiments of the presently disclosedsubject matter.

FIG. 11 is a line graph showing nanoparticle excretion over time.

FIG. 12A-121 are fluorescent microscope images for normal mice and fortumor-infected mice.

DETAILED DESCRIPTION

The presently disclosed subject matter is presented with sufficientdetails to provide an understanding of one or more particularembodiments of broader inventive subject matters. The descriptionsexpound upon and exemplify particular features of those particularembodiments without limiting the inventive subject matters to theexplicitly described embodiments and features. Considerations in view ofthese descriptions will likely give rise to additional and similarembodiments and features without departing from the scope of theinventive subject matters.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which the presently disclosed subject matter pertains.Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresently disclosed subject matter, representative methods, devices, andmaterials are now described.

Following long-standing patent law convention, the terms “a,” “an,” and“the” refer to “one or more” when used in the subject specification,including the claims. Thus, for example, reference to “a nanoparticle”can include a plurality of such nanoparticles, and so forth.

Unless otherwise indicated, all numbers expressing quantities ofcomponents, conditions, and so forth used in the specification andclaims are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the instant specification and attachedclaims are approximations that can vary depending upon the desiredproperties sought to be obtained by the presently disclosed subjectmatter.

As used herein, the term “about,” when referring to a value or to anamount of mass, weight, time, volume, concentration, and/or percentagecan encompass variations of, in some embodiments ±20%, in someembodiments ±10%, in some embodiments ±5%, in some embodiments ±5%, insome embodiments ±0.5%, and in some embodiments ±0.1%, from thespecified amount, as such variations are appropriate in the disclosedpackages and methods.

In some embodiments, the presently disclosed subject matter provides alow toxicity water soluble carbon nanoparticle comprising a plurality ofgraphene sheets of diameter ranging from about 40 nm to 120 nm in theclosed or spherical form. The uniquely sized graphene oxidenanoparticles are produced from wood charcoal, low grade coal, and/orcarbonized plant biomass in an eco-friendly method. In some embodiments,the graphene oxide is also referred to herein as a water soluble carbonnanoparticle (wsCNP). The graphene oxide nanoparticles produced hereinare significantly smaller than the micrometer-sized graphene oxidenanoparticles produced by prior art methods (e.g., Hummers, W. S. et al.[1]), but larger than the 20 nm-sized graphene quantum dot produced fromanthracite coal (Ye., R. et al. [4]) and the water soluble graphenequantum dots (wsCdot) produced by a process described in U.S. Pat. No.8,357,507 (where the diameter of the wsCdot is limited to about 2 nm to20 nm). The graphene oxide nanoparticles provided herein comprise adiameter of about 40 nm to about 120 nm in the closed or spherical form,which is believed to be an ideal size for delivery of therapeutic agentsand/or imaging agents to a subject.

As used herein the term “water soluble” refers to the physical propertydescribing the ability of the disclosed wsCNP to dissolve in solventwater. While the disclosed graphene oxide nanoparticles and the wsCdotsof the '507 patent are produced using different methods, both have aplurality of carboxylate groups on the graphene sheets that are believedto contribute to water solubility. Differing compositions dissolve atdiffering rates, but in general the dissolution rate of the wsCNP of thepresently disclosed subject matter is at least 1 mg per mL of water. Inaddition, both the graphene oxide nanoparticles produced according tothe method provided herein and the wsCdots of the '507 patent naturallyfluoresce. “Fluorescing,” as used herein, refers to the wsCNPself-capability to produce a luminescence upon release of energy afterbeing exposed to a photon source of a given wavelength. Typically,fluorescence occurs at a different wavelength than the excitationwavelength of photons used to create the fluorescence.

It has been discovered that naturally pre-formed graphene oxide can beisolated from low grade coal, wood charcoal, and/or carbonized plantbiomass by leaching the graphene oxide with dilute sodium hydroxide. Incontrast to the method described in the '507 patent, strong acid is notrequired for preparation of the graphene oxide nanoparticles disclosedherein. “Low grade coal” refers to coal typically found in open pits,not deeply buried as required by higher grade coal (such as, forexample, anthracite that requires completely anaerobic and hightemperature conditions to extract graphene oxide [5]). In someembodiments, low grade coal includes non-coking coal and bituminouscoal. Non-coking coal in general has a high ash and moisture content.For example, in some embodiments the low grade coal of the presentlydisclosed subject matter includes coal with heat value of between about1300-4200 Kcal/kg, gross calorific value at 5% moisture of between about3113-5089 kcal/kg, and percentage ash plus moisture at 60% RH and 40° C.from about 34-55%.

As used herein, the term “carbonized plant biomass” refers to coalproduced by the transformation of structured molecules of wood andcellulose products in plant biomass through the elimination of water andvolatile substances. In some embodiments, carbonized plant biomass caninclude wood coal or vegetal coal.

In some embodiments, the presently disclosed subject matter provideswater soluble carbon nanoparticles (wsCNP) having a plurality ofgraphene sheets of diameter ranging from about 2 nm to about 120 nm inclosed form that can be loaded with a molecule (such as, but not limitedto, a therapeutic agent or an imaging agent) for delivery to a subject[9]. In some embodiments, the disclosed wsCNPs have a lower toxicitythan those produced from anthracite coal. The wsCNP are herein shown tochange form based on changes in pH between an open form and a closedform that is spherical in shape. The structure change can be exploitedto encapsulate a drug molecule within the spherical form such that theentrapped molecule is not released (even during sonication). As setforth herein below, a slight change in pH enables the closed form(spherical form) to open such that the molecule inside is released. Theintracellular pH of around 6.8 and the extracellular pH of around 7.4 ofmammalian cells coincides with the pH dependency of the structuralchange of the disclosed wsCNP. Thus, the disclosed wsCNP can be loadedwith a molecule of interest (i.e., a therapeutic agent), the loadedwsCNP can be delivered to a subject, and the molecule of interest can bereleased within a subject for treatment.

In some embodiments, the presently disclosed subject matter is directedto a method of making graphene oxide. Particularly, the method comprisestreating wood charcoal, low grade coal, and/or carbonized plant biomasswith a dilute alkali solution. The method further comprises separatingthe alkali solution from the insoluble material and neutralizing thesolution, wherein a precipitate that occurs after neutralizationincludes a plurality of graphene oxide nanoparticles having a pluralityof sheets ranging in size from about 40 nm to 200 nm in the open form.In some embodiments, the method comprises separating the precipitatethat appears after neutralization using centrifugation. In someembodiments, the yield of the precipitate containing the GO can rangefrom about 8-12% based on the source material used. The GO produced bythe disclosed method is freely soluble in alcohol and in water aboveneutral pH. In some embodiments, the GO produced by the disclosed methodcan be less soluble in the aqueous-acidic pH range.

In some embodiments, the wood charcoal, low grade coal, and/orcarbonized plant biomass can be pulverized or otherwise ground into afiner particle or powdered form prior to treating in the dilute alkalisolution. In some embodiments, the wood charcoal, low grade coal, and/orcarbonized plant biomass can be freed from aromatic hydrocarbons andother associated soluble organic compounds by washing with an organicsolvent (such as, but not limited to, toluene and/or acetone) prior totreatment in the dilute alkali solution. For example, thorough washingof carbonized plant biomass with acetone can be used to remove aromatichydrocarbons prior to treating in the dilute alkali solution. In someembodiments, the wood charcoal, low grade coal, and/or carbonized plantbiomass can be washed with dilute acid (i.e., hydrochloric acid) and/orwater before and/or after washing with organic solvent. In someembodiments, the material can be dried (air dried, for example) prior totreating in the dilute alkali solution. As used herein, the dilutealkali solution can include any water-soluble hydroxide orcarbonate/bicarbonate (e.g., sodium or potassium hydroxide, sodium orpotassium bicarbonate, and/or a solution of ammonia in water). In someembodiments, the dilute alkali solution can range in concentration fromabout 5% to about 30%, depending on the source of material used. In someembodiments, the dilute alkali solution can be a 10% sodium hydroxidesolution.

In some embodiments, treatment in dilute alkali solution can beperformed at a temperature ranging from about 25° C. to 40° C. However,it is to be understood that in some embodiments, the treatment can beperformed at higher temperatures (such as, but not limited to,temperatures of up to about 80° C.) where the method for producing thegraphene oxide nanoparticles can be completed in a lesser timeframe. Insome embodiments, treating with dilute alkali solution can be performedat a temperature of about 40° C.

In some embodiments, treating with dilute alkali solution can beperformed until the solution turns a yellow-brown color. In someembodiments, treating with dilute alkali solution can be performed untilthere is no longer significant observable additional leaching from thematerial.

In some embodiments, the solution can be neutralized to a pH of about 7.In some embodiments, the solution can be neutralized with a mineralacid, such as (but not limited to) a dilute mineral acid. As usedherein, “mineral acid” refers to any mineral acid including (but notlimited to) hydrochloric acid, sulfuric acid, and/or nitric acid. Insome embodiments, the precipitate that occurs after neutralization ofthe solution can appear slowly upon standing. The precipitate thatoccurs after neutralization of the solution includes graphene oxidenanoparticles having a plurality of sheets ranging in size from about 40nm to 200 nm in the open form. In some embodiments, the method caninclude washing the precipitate with cold water.

In some embodiments, the presently disclosed subject matter is directedto a method of making graphene oxide nanoparticles, the methodconsisting essentially of treating a material including one or acombination of wood charcoal, low grade coal, or carbonized plantbiomass in an alkali solution, wherein the precipitate that appearsafter neutralization of the solution comprises graphene oxidenanoparticles having a plurality of sheets ranging in size from about 40nm to 200 nm in the open form. In some embodiments, the solution can beneutralized to a pH of about 7 (e.g., with a mineral acid such ashydrochloric acid). In some embodiments, the alkali solution can be 10%sodium hydroxide solution. In some embodiments, the treating in alkalisolution can be performed at a temperature ranging from about 25° C. to40° C., such as about 40° C. In some embodiments, the treating in alkalisolution can be performed until the solution turns a yellow-brown color.In some embodiments, the wood charcoal, low grade coal and/or carbonizedbiomass can be in a powdered form. In some embodiments, the woodcharcoal, low grade coal and/or carbonized biomass can be essentiallyfree of aromatic hydrocarbons and other associated soluble organiccompounds. In some embodiments, the method can include washing theprecipitate with cold water.

As set forth below in Example 1 and in FIG. 1-4, freshly prepared GOmaterial produced from the disclosed method comprise a plurality ofgraphene sheets in an “open” form, where the majority of the sheets havea size ranging from about 40 nm to 200 nm, as observed by DLS, AFM, andSEM. In addition, the GO produced by the disclosed method is freelysoluble in alcohol and in water above neutral pH and is somewhat lesssoluble in the aqueous-acidic pH range. To this end, FIG. 1A illustratesa size distribution of GO determined using DLS. Upon aging overnight, inacidic pH 6.8), or after drying under vacuum, the structure of the GOwas observed to change from oblique arches like a palm of a hand (i.e.,the “open structure”) to a clenched fist-like structure (i.e., the“closed structure”) of a generally spherical shape. The closed structurewas shown to revert back to the open form at pH of 7.4.

The change in structure of the GO was also observed in the electronicspectra shown in FIGS. 1B and 10. Particularly, FIG. 1B is an electronicspectra of GO (solid line for freshly prepared GO; dotted line for agedGO). FIG. 10 is an electronic spectrum of the GO in PBS buffer pH 6.8(solid line) and PBS buffer pH 7.4 (dotted line). At pH 6.8, theabsorption at 260 nm shows a distinctive peak, but at pH 7.4 the contourof the peak appears as a shoulder. The changes to the absorptionfeatures are similar to those observed with the aged GO sample inalcohol. The spectra cross points when the GO is present at pH 6.8versus when it is present at pH 7.4. The distinct change in theelectronic spectra can be used as a marker to identify the twostructural forms, namely the open (basic pH) and closed (spherical;acidic pH) forms.

The change in structure of the GO from an “open” type of form (freshlyprepared GO and GO at a pH of about 7.2 and greater) to a “closed” typeof form that is generally spherical in shape (GO after aging a few hoursat room temperature, GO subjected to temperature change, GO after dryingunder a vacuum, including drying under a vacuum at −37° C., and GO at apH of about 6.8 and less) is referred to herein for the purposes of thespecification and claims in a number of different ways. Specifically,the “open” form GO can be referred to herein by any of the followingterms: “open,” “open form,” “open fist,” “open fisted,” “oblique archlike a palm of a hand,” “oblique arch,” “oblique arch form,” “openstructure form,” and “open structure.” Similarly, the “closed” form GOcan be referred to herein by any of the following terms: “closed,”“closed form,” “spherical,” “spherical form,” “generally spherical,”“generally spherical shape,” “closed fist,” “closed fisted,” “clenchedfist,” and “clenched first form.”

FIG. 2 shows a series of microscopic images (AFM, SEM, TEM and HRTEM) ofopen GO and closed GO, illustrating the open form of the fresh GO andthe GO at basic pH and the closed or spherical form of the GO afteraging and at acidic pH. Particularly, FIG. 2A is an Atomic ForceMicroscopy (AFM) image of open fisted GO; FIG. 2B is an AFM image ofaged close fisted GO; FIG. 2C is a Scanning Electronic Microscopy (SEM)image of GO open first form upon exposure with ammonia vapor; FIG. 2D isan SEM image of close fisted GO; FIG. 2E is a High ResolutionTransmission Electron Microscopy (HRTEM) image of open first GO; andFIG. 2F is an HRTEM image of closed first GO.

Without being limited to any specific mechanism of action, the GOnanoparticles are believed to convert between the closed and open formsas a result of an epoxidediol inter-conversion. Particularly, the closedGO is roughly spherical in form and can be expected to bethermodynamically more stable than the open first form. It is believedthat several adjacent phenolic hydroxyl groups on the surface of the GOparticipate in epoxide formation, resulting in the creation of anoblique arch (like a palm of a hand) that can close to a spherical form.The hypothesis was tested by the deuterolysis of the GO in ‘closed fist’form. Specifically, the GO was treated with NID₄OD—D₂O and dried undervacuum at −37° C., as set forth in FIG. 3A-3C that illustrate Fouriertransform infrared spectroscopy (FT-IR) of the GO. FIG. 3A shows theFTIR spectra of the open fisted GO form after treatment in NH₄OH—H₂O anddrying under vacuum at −37° C. (due to the presence of the NH₄OH—H₂O,the GO remains in the open form after vacuum drying). FIG. 3B shows theFTIR spectra for GO treated with dilute hydrochloric acid and evaporatedunder vacuum. FIG. 3C shows the FTIR spectra of GO treated withND₄OD—D₂O and dried under vacuum at −37° C. The spectra in FIG. 3A showsan absence of epoxide vibration with the appearance of a common v(OH)vibration for dial merged with the v(OH) vibration from carboxylic acidgroup. FIG. 3C shows the appearance of v(OD) around 2600 cm⁻¹ and alsoshows the disappearance of a peak around 1000 cm⁻¹, responsible for theepoxide vibration (C—O—C) [6]. When GO was treated with dilutehydrochloric acid and evaporated under vacuum, a (C—O—C) vibrationaround 1000 cm⁻¹ (FIG. 3B) was observed; the peak was not apparent inthe spectra of FIG. 3A or 3C. In FIG. 3A, which is a spectrum of the GOwhen treated with NH₄OH—H₂O and dried under vacuum at −37° C., anepoxide vibration was not observed, but there was a vOH at 3500 cm⁻¹,indicating an open fisted form of the GO under basic (NH₄OH—H₂O)conditions. FIG. 3B shows an epoxide vibration (C—O—C) around 1000 cm⁻¹and the presence of vOH at 3500 cm⁻¹. In FIG. 3C, the GO was treatedwith ND₄OD—D₂O and dried under vacuum at −37° C., and the spectraconfirms the epoxidediol inter-conversion (presence of epoxidevibration) and shows appearance of vOD around 2600 cm⁻¹ anddisappearance of a peak around 1000 cm⁻¹. Accordingly, it can beconfirmed that the open first form of GO is present in the ND₄OD—D₂O.Further, the addition of ND₄OD—D₂O opens the GO closed first form, whichis shown in the FTIR spectra of FIG. 3C.

Without desiring to be limited to any particular mechanism of action, itis believed that the π-π stacking in the honeycomb hexagon structure ofcarbon in graphene is counteracted with the introduction of severaloxo-functional groups on the surface of GO. The larger surface grapheneoxide area of the GO resulting from the disclosed method (as comparedto, for example, the wsCdots of the '507 patent where the size islimited to within 20 nm) would be expected to respond to energy savingsand result in a stable clenched first (spherical) form. A size range of40 nm to 200 nm with maximum distribution in the range of about 60-140nm was determined for the open form of the GO using DLS analysis (FIG.1A). The size of the open form of the GO was also measured by AFM (FIG.4A). These data were used to calculate the expected size of the closedGO sphere structure formed by either two open first graphene sheets (twosuperficial halves) combining at the edges to form a spherical shape orby closure of a single graphene sheet. The results are shown in Table 1below. The AFM data are shown in the histogram size distribution graphsof FIG. 4A (size distribution of GO in the open first structure) andFIG. 4B (size distribution of GO in the closed fist, sphericalstructure). The range of size distribution observed for the open andclosed first forms of GO using AFM indicates the possibility of either asingle sheet closure or closure of two or more sheets and the closedspherical form is energetically favored.

TABLE 1 Calculation of Size Distribution of Closed Form GO Number ofUnits Required to Form Closed GO (Spherical) Open GO 1 2 Length BreadthArea Size of Closed GO (nm) (nm) (nm²) (diameter in nm) 151.741 96.59914658.03 70 100 131.06 79.598 10432.11 60 80 151.702 93.153 14131.5 70100 182.764 110.328 20163.99 80 120 144.847 100.223 14517 70 100 151.741103.433 15695.03 70 100 172.423 113.776 19617.6 80 110 106.881 93.1539956.286 55 80 151.702 93.09 14121.94 70 100 120.672 89.708 10825.24 6080 144.847 106.936 15489.36 70 100 104.348 82.746 8634.38 50 70 77.78572.403 5631.867 40 60

In some embodiments, a material is provided having graphene oxidenanoparticles (GO) produced by the method disclosed herein.Particularly, the method comprises treating a material including one ora combination of wood charcoal, low grade coal, or carbonized plantbiomass in a dilute alkali solution. The method further comprisesseparating the solution from the insoluble material and neutralizing thesolution, wherein a precipitate that appears after neutralization of thesolution comprises graphene oxide nanoparticles having a plurality ofsheets ranging in size from about 40 nm to 200 nm in the open form. Insome embodiments, the solution can be neutralized (i.e., using a mineralacid such as hydrochloric acid) at a pH of about 7. In some embodiments,the dilute alkali solution can be a 10% sodium hydroxide solution. Insome embodiments, treating in dilute alkali solution can be performed ata temperature of about 25° C. to 40° C., such as about 40° C. In someembodiments, treating with dilute basic solution can be performed untilthe solution turns a yellow-brown color. In some embodiments, the woodcharcoal, low grade coal or carbonized biomass can be in a powderedform. In some embodiments, the wood charcoal, low grade coal orcarbonized biomass can be essentially free of aromatic hydrocarbons andother associated soluble organic compounds.

In some embodiments, a material is provided comprising graphene oxidenanoparticles (GO), wherein the material is produced using a methodconsisting essentially of treating the material (including one or acombination of wood charcoal, low grade coal, or carbonized plantbiomass) in an alkali solution. A precipitate that appears afterneutralization of the solution comprises graphene oxide nanoparticleshaving a plurality of sheets ranging in size from about 40 nm to 200 nmin the open form.

In some embodiments, the solution can be neutralized at a pH of about 7,such as by using a mineral acid (e.g., hydrochloric acid) at a pH ofabout 7. In some embodiments, the alkali solution can be 10% sodiumhydroxide solution. In some embodiments, the treating in alkali solutioncan be performed at a temperature of about 25° C. to 40° C., such about40° C. In some embodiments, the treating in alkali solution can beperformed until the solution turns a yellow-brown color. In someembodiments, the wood charcoal, low grade coal or carbonized biomass canbe in a powdered form. In some embodiments, the wood charcoal, low gradecoal or carbonized biomass can be essentially free of aromatichydrocarbons and other associated soluble organic compounds.

In some embodiments, a material is provided including graphene oxidenanoparticles (GO), wherein the GO includes a plurality of graphenesheets, wherein a majority of the graphene sheets have a diameter whenpresent in a closed form ranging from about 40 nm to 120 nm, and whereinthe graphene sheets have a plurality of carboxylic and hydroxyl groupson the plurality of sheets. In some embodiments, the carboxylic groupscomprise at least about 20% of the total weight of the GO. In someembodiments, the GO can demonstrate solubility in aqueous solution at aconcentration of about 1 mg GO/mL. In some embodiments, the GO candisplay fluorescence in the blue, green, red, and infra-red spectra. Insome embodiments, the GO can have amphiphilic properties.

Based on the observation of the reversible structural change between theopen and closed forms of the GO resulting from pH change, the ability ofthe GO to load and release a molecule (such as a therapeutic molecule)was investigated. For these studies, the molecules tetraphenyporphyrin(TPP) and donepezil were selected. Both TPP and donepezil are spectrallyidentifiable molecules, and TPP is considered to be a large therapeuticmolecule. In addition, TPP is considered a model for several porphyrinsin photodynamic therapy [7]. Donepezil is an acetylcholinesteraseinhibitor commonly used for the treatment of Alzheimer's disease.

Encapsulation of each molecule within the GO was performed as describedbelow in Example 2. Particularly, the method for encapsulation includescontacting a GO in an open form (such as, for example, a freshlyprepared GO or a GO at a pH of about 7.2 or greater) with a molecule tobe encapsulated in an aqueous or alcoholic solution. The GO can beevaporated to dryness under vacuum at −37° C., can be left to age, orcan be placed at a pH of about 6.8 or lower, resulting in the structuralchange to the closed form and encapsulation of the molecule. The GOcomprising the encapsulated molecule is referred to herein as a GOcomposite such as, for example, a “GO-TPP” composite or a “GO-donepezil”composite. In some embodiments, the GO composite can be washed with, forexample, water, a dilute acidic solution, or alcohol. In someembodiments, the GO composite can be further extracted with alcohol andevaporated to dryness under vacuum at −37° C.

The GO-TPP and GO-donepezil composites produced as described in Example2 were subjected to various spectroscopic and microscopic investigationsand the results are shown in FIGS. 5 and 6. Both TPP and donepezil areinsoluble in water. FIG. 5A is an HRTEM image of the GO-TTP compositeafter treatment with NH₃ to increase the pH, which shows the GO in theopen form. FIG. 5B is an HRTEM image of the GO-TPP, showing the GO inthe closed form. The inset of FIG. 5B is an enlarged section of thecomposite that shows the presence of stacked TPP within the GO. FIG. 5Cis an SEM image of a GO-TPP composite after treatment with NH₃ toincrease the pH and shows the GO in the open form. FIG. 5D is an SEMimage of a GO-TPP composite and shows the GO in the closed form. FIG. 5Eis an electronic spectra of a GO-TPP composite in PBS buffer pH 7.4,showing the open form of the GO that allows for release of TPP (inset:electronic spectrum of dichloromethane extract of the GO-TPP buffershowing the features of TPP). FIG. 5F is an electronic spectra of theGO-TPP in PBS buffer at pH 6.8, showing features of the encapsulated TPPwithin the closed form (TPP was not detected after dichloromethaneextraction of the GO-TPP buffer). FIG. 5G is an electronic spectra ofthe GO-donepezil composite in PBS buffer pH 7.4, showing the open formof GO allows for release of the donepezil (inset: electronic spectrum ofdichloromethane extract of the GO-donepezil buffer showing the featuresof donepezil). FIG. 5H is an electronic spectra of the GO-donepezilcomposite in PBS buffer pH 6.8, showing features of the encapsulateddonepezil within the closed form of the GO (donepezil was not detectedafter dichloromethane extraction of the GO-donepezil buffer).

Powder X-ray diffraction (XRD) was performed on the GO-TPP, as shown inFIG. 6A-6C. Particularly, FIG. 6A is an XRD spectrum of GO withoutencapsulated TPP. FIG. 6B is an XRD spectrum of GO-TPP composite,showing sharp peaks for TTP and the broad peaks of the GO. FIG. 6C is anenlarged view of the spectrum from FIG. 6B to more clearly illustratethe presence of both the broad peaks from the GO and the sharp peaksfrom the TPP.

In addition to encapsulation of the GO with a molecule, theencapsulation method disclosed herein can also be used with othergraphene-based water soluble carbon nanoparticles (wsCNPs). For example,the water soluble quantum carbon dots (wsCdot) described in the '507patent (herein incorporated by reference in its entirety) were used toencapsulate donepezil, as described in Example 2 and shown in FIG. 7.The wsCdots described in the '507 patent have a size range of about 2-20nm in diameter. As set forth in Example 2, the wsCdot was preparedaccording to the methods described in the '507 patent and investigatedusing microscopic and electronic spectral measurements as describedherein above for the GO. FIG. 7B is an SEM image of aged wsCdot. FIG. 7Bis an SEM image of aged wsCdot after exposure to NH₃ vapour, showing achange from a spherical structure to an open structure after the NH₃treatment. FIGS. 7C and 7D are electronic spectra of a wsCdot-donepezilcomposite prepared according to the encapsulation method of the presentdisclosure. FIG. 7C shows electronic spectra of the wsCdot-donepezilcomposite in PBS, pH 6.8, where extraction with DCM did not remove thedonepezil from the composite. FIG. 7D shows electronic spectra of thewsCdot-donepezil composite in PBS, pH 7.4, where extraction with DCMrevealed a signature donepezil spectrum which is shown in the inset.Accordingly, the encapsulation methods of the present disclosure areuseful with wsCNP having a plurality of graphene sheets, wherein thegraphene sheets have a plurality of carboxylic and hydroxyl groups.

In some embodiments, the presently disclosed subject matter is directedto a method reversible encapsulation of a molecule within a watersoluble carbon nanoparticle (wsCNP). Particularly, the method comprisescontacting a wsCNP in an open form with a molecule to be encapsulatedwithin the wsCNP in a solution. The wsCNP comprises a plurality ofgraphene sheets that include a plurality of carboxylic and hydroxylgroups. The wsCNP has a closed form at a subsequent time such that theencapsulated molecule can be released from the closed form wsCNP uponexposure to a pH of about 7.2 or greater. In some embodiments, thecarboxylic groups can comprise at least about 20% of the total weight ofthe wsCNP. In some embodiments, the solution can be an aqueous oralcoholic solution.

The open form of wsCNP refers to freshly prepared wsCNP, wsCNP at a pHof about 7.2 or greater, and wsCNP in the open form as characterizedherein by microscopic and electronic analysis. As used herein, thephrase “wherein the wsCNP has a closed form at a subsequent time” refersto the data set forth in the presently disclosed subject matter thatillustrates that aging at room temperature can result in the wsCNPchanging from an open form to a closed form, that subjecting a wsCNP toa temperature change can result in changing from an open form to aclosed form, drying a wsCNP under a vacuum (including drying under avacuum at −37° C.) can result in the wsCNP changing from an open form toa closed form, and/or placing a wsCNP at a pH of about 6.8 or less canresult in the wsCNP changing from an open form to a closed form. In someembodiments, the phrase “wherein the wsCNP has a closed form at asubsequent time” refers to any method that causes or allows for a wsCNPto change structure to a closed form as characterized herein bymicroscopic and electronic analysis.

The presently disclosed method of reversible encapsulation can furtherinclude removing a majority of the molecule that is not encapsulatedwithin the closed form wsCNP. Specifically, removing a majority of themolecule that is not encapsulated within the closed form wsCNP caninclude washing the wsCNP with water, a dilute acid, an alcohol, and/ora solvent. In some embodiments, the method can include drying the wsCNPand/or extracting the wsCNP with an alcohol.

In some embodiments of the presently disclosed method of reversibleencapsulation, a majority of the graphene sheets present in the closedform can have a diameter ranging from about 2 nm to 120 nm. In someembodiments, a majority of the graphene sheets present in the closedform can have a diameter ranging from about 40 nm to 120 nm.

In some embodiments of the presently disclosed method of reversibleencapsulation, the wsCNP can be produced by a process comprisingtreating a material comprising one or a combination of wood charcoal,low grade coal, and/or carbonized plant biomass in a dilute alkalisolution; and separating the solution from the insoluble material andneutralizing the solution, wherein a precipitate that appears afterneutralization of the solution comprises graphene oxide nanoparticleshaving a plurality of sheets ranging in size from about 40 nm to 200 nmin the open form.

In some embodiments of the presently disclosed method of reversibleencapsulation, the wsCNP can be produced by a process consistingessentially of treating a material including one or a combination ofwood charcoal, low grade coal, and/or carbonized plant biomass in analkali solution, wherein a precipitate that appears after neutralizationof the solution comprises graphene oxide nanoparticles having aplurality of sheets ranging in size from about 40 nm to 200 nm in theopen form. In some embodiments of the presently disclosed method ofreversible encapsulation within the wsCNP, DNA can be encapsulatedwithin GO as described in Example 2. Particularly, calf thymus DNA wasmixed with an aqueous-alcoholic solution of GO, and the resultant clearsolution was vacuum dried at −37° C. yielding GO-DNA composite. Thecomposite was washed with cold water to remove free DNA not encapsulatedwithin the wsCNP. Electronic spectra were compared in PBS at pH 6.5 forthe DNA alone, GO alone, and the GO-DNA composite dissolved in thebuffer. FIG. 8A illustrates the electronic spectra for the calf thymusDNA alone, showing a peak at 259 nm. FIG. 8B is the electronic spectrafor the GO alone. FIG. 8C is the electronic spectra for the GO-DNAcomposite, showing the characteristic absorption peak of DNA at 259 nmand also showing the background absorption of the GO. FIG. 8A-8Cdemonstrate that fragments of DNA or other types of nucleic acidmolecules (such as those encoding a gene of interest or a siRNA, forexample), can be encapsulated in the wsCNP.

In some embodiments, a wsCNP can be encapsulated with any of thelanthanides. It should be appreciated that lanthanides are useful asimaging agents and sensors. For the encapsulation, one or morelanthanides can be mixed with an aqueous or alcoholic solution of wsCNPin the open form. A structural change in the wsCNP to a closed form canbe allowed for, wherein the encapsulated lanthanide can be released fromthe closed form wsCNP upon exposure to a pH of about 7.2 or greater. Insome embodiments, the closed form wsCNP can be washed to remove freelanthanide not encapsulated within the wsCNP.

In some embodiments of the disclosed method of reversible encapsulation,the molecule is an imaging agent and/or a therapeutic agent, such as(but not limited to) a therapeutic agent for the treatment of cancer. Insome embodiments, the molecule can be donepezil, TPP, a protein, apeptide, a small molecule, a nucleic acid, a single strand DNA, a doublestrand DNA, an RNA, an siRNA, an oligonucleotide, a gene, a genefragment, an imaging agent, and/or a lanthanide.

In some embodiments, the molecule can be a therapeutic agent for thetreatment of a brain disorder, including (but not limited to dementia,vascular dementia, and/or Alzheimer's disease). In some embodiments, themolecule can be a therapeutic agent for delivery in a subject across theblood brain barrier (BBB).

In some embodiments, a method is provided for using the wsCNP to crossthe blood brain barrier (BBB). An experiment is described in Example 3in which wsCNP was injected into the tail of transgenic mice. Thetransgenic mice have pericyte dysfunction, associated withneurodegenerative diseases. Pericyte function is an important componentof the neurovascular unit that contributes to the integrity of the BBB.BBB disruption or disintegrity in the affected the brain can allow forpassive diffusion. By intravenous administration of the wsCNP to amouse, it was demonstrated that the fluorescent wsCNP smoothly crossedthe BBB into the brain of transgenic FVBN mice. FIG. 9 shows an image ofthe mouse brain in which the wsCNP has crossed the BBB into the brain.In FIG. 9, each of the tumor cells, blood vessels, and wsCNP areindicated with arrows, showing the ability of the wsCNP to cross theBBB. Importantly, prior art methods make use of passive diffusion oractive transport. Passive diffusion includes fat-soluble substancesdissolve (amphiphilic) in the cell membrane and cross the BBB (e.g.,alcohol, caffeine, nicotine). Active transport includes substances thatthe brain needs, such as glucose and amino acids, that are carriedacross the BBB by special transport proteins (i.e., specific receptors,protein mediated). The presently disclosed nanoparticles, however, insome embodiments operate through receptor-mediated transport, whereinmolecules link up to receptors on the surface of the brain and areescorted through (e.g., insulin). Thus, a key differentiator of thedisclosed nanoparticles is that they have the ability to carry any drugthrough the BBB.

In some embodiments of reversible encapsulation of molecules within thewsCNP, the wsCNP can further include one or more biomolecules ordivalent metals to target delivery of the wsCNP to a cell, tissue,brain, or organ. The biomolecule can be one or a combination of aprotein, a receptor, an aptamer, a ligand, or an antibody. The divalentmetal can be manganese. For example, Example 4 describes incorporationof manganese (Mn) or another divalent metal into the wsCNP to allow fortargeting of the wsCNP to the brain. In this manner, the wsCNPcontaining Mn can utilize the capacity of Mn to be taken up by nerveterminals via the bivalent metal transporter of the olfactory nerveswhere it can be further transported to the entire brain (see, forexample, International Patent Application Publication WO 2013/040295which is hereby incorporated by reference in its entirety). In a firstexperiment, manganese acetylacetonate (Mn(acac)₃) was incorporated intothe GO produced according to the method in Example 1 by mixing the GOand Mn(acac)3 in ethanol. The solution was vacuum dried at −37° C.resulting in a solid powder form. The powdered mass was washed withdistilled water to remove any excess Mn(acac)₃. FIG. 10A-10D showelectronic spectra of the: (A) Untreated GO in ethanol; (B) Mn(acac)₃ inethanol; (C) GO containing Mn(acac)₃; and (D) Simulated spectra ofcombined GO and Mn(acac)₃. The spectral data show that the Mn remainsassociated with the GO at the pH 6.5. This experiment is an exampleshowing that a bivalent metal such as Mn can be incorporated into thewsCNP to take advantage of the metal transporter to target delivery ofthe wsCNP to the brain. Thus, wsCNP can be loaded with a therapeuticagent and/or an imaging agent and also contain incorporated divalentmetal to advantage of the metal transporter to target delivery of thewsCNP contents to the brain of a subject.

In some embodiments, the presently disclosed subject matter is directedto a water soluble carbon nanoparticle (wsCNP) comprising a moleculeencapsulated therein. In some embodiments, the wsCNP can include aplurality of graphene sheets in a closed form at a pH of about 6.8 orless. In some embodiments, a molecule is encapsulated within the closedform wsCNP, wherein a plurality of carboxylic and hydroxyl groups arepresent on the plurality of sheets, and wherein the molecule can bereleased from the closed form wsCNP at a pH of about 7.2 and higher. Insome embodiments, the carboxylic groups can comprise at least about 20%of the total weight of the wsCNP. In some embodiments, the wsCNP canhave a solubility in aqueous solution at a concentration of about 1 mgwsCNP/mL. In some embodiments, the wsCNP can display fluorescence in theblue, green, red, and infra-red spectra. In some embodiments, the wsCNPcan have amphiphilic properties.

In some embodiments, a majority of the graphene sheets present in theclosed form wsCNP having a molecule encapsulated therein has a diameterranging from about 2 nm to 120 nm. In some embodiments, a majority ofthe graphene sheets present in the closed form wsCNP having a moleculeencapsulated therein has a diameter ranging from about 40 nm to 120 nm.

In some embodiments, the wsCNP comprising a molecule encapsulatedtherein can be produced by a method including: treating a materialcomprising one or a combination of wood charcoal, low grade coal, orcarbonized plant biomass in a dilute alkali solution; and separating thesolution from the insoluble material and neutralizing the solution,wherein a precipitate that appears after neutralization of the solutioncomprises graphene oxide nanoparticles having a plurality of sheetsranging in size from about 40 nm to 200 nm in the open form.

In some embodiments, the wsCNP having a molecule encapsulated thereincan be produced by a process consisting essentially of treating amaterial including one or a combination of wood charcoal, low gradecoal, or carbonized plant biomass in an alkali solution, wherein aprecipitate that appears after neutralization of the solution comprisesgraphene oxide nanoparticles having a plurality of sheets ranging insize from about 40 nm to 200 nm in the open form.

In some embodiments, the process for producing the wsCNP having amolecule encapsulated therein can further include washing theprecipitate with cold water.

In some embodiments, the molecule encapsulated within the wsCNP can bean imaging agent and/or a therapeutic agent, such as a therapeutic agentfor the treatment of cancer. In some embodiments, the moleculeencapsulated within the wsCNP can be a therapeutic agent for thetreatment of a brain disorder, such as (but not limited to) dementia,vascular dementia, and/or Alzheimer's disease.

In some embodiments, the molecule encapsulated within the wsCNP can beDonepezil, TPP, a protein, a peptide, a small molecule, a nucleic acid,a single strand DNA, a double strand DNA, an RNA, an siRNA, anoligonucleotide, a gene, a gene fragment, an imaging agent, and/or alanthanide.

In some embodiments, the molecule encapsulated within the wsCNP can befor delivery in a subject across the blood brain barrier (BBB). In someembodiments, the wsCNP having a molecule encapsulated therein canfurther include one or more biomolecules or divalent metals to targetdelivery of the wsCNP with the encapsulated molecule to a cell, tissue,brain, and/or organ. In some embodiments, the biomolecule can be aprotein, a receptor, an aptamer, a ligand, and/or an antibody. In someembodiments, the divalent metal can be manganese. In some embodiments,the cell can be a cancer cell.

In some embodiments, the presently disclosed subject matter is directedto a method of delivering a molecule to a subject. Particularly, themethod comprises delivering to the subject a composition including awater soluble carbon nanoparticle (wsCNP) having the moleculeencapsulated therein, wherein the encapsulated molecule is released fromthe wsCNP into the subject as a result of the increase in pH afterdelivery to the subject's body.

In some embodiments, the wsCNP can include a plurality of graphenesheets in the closed form at a pH of about 6.8 or less, wherein themolecule is encapsulated within the closed form wsCNP, and wherein aplurality of carboxylic and hydroxyl groups are present on the pluralityof sheets. In some embodiments, the carboxylic groups can comprise atleast about 20% of the total weight of the wsCNP. In some embodiments,the wsCNP can have a solubility in aqueous solution at a concentrationof about 1 mg wsCNP/mL. In some embodiments, the wsCNP can displayfluorescence in the blue, green, red, and infra-red spectra. In someembodiments, the wsCNP can have amphiphilic properties.

In some embodiments, a majority of the graphene sheets present in theclosed form wsCNP having a molecule encapsulated therein can have adiameter ranging from about 2 nm to 120 nm, such as from about 40 nm to120 nm.

In some embodiments, the wsCNP having a molecule encapsulated thereincan be produced by a process including: treating a material comprisingone or a combination of wood charcoal, low grade coal, or carbonizedplant biomass in a dilute alkali solution; and separating the solutionfrom the insoluble material and neutralizing the solution, wherein aprecipitate that appears after neutralization of the solution comprisesgraphene oxide nanoparticles having a plurality of sheets ranging insize from about 40 nm to 200 nm in the open form.

In some embodiments, the wsCNP having a molecule encapsulated thereincan be produced by a process consisting essentially of treating amaterial including one or a combination of wood charcoal, low gradecoal, or carbonized plant biomass in an alkali solution, wherein aprecipitate that appears after neutralization of the solution includesgraphene oxide nanoparticles having a plurality of sheets ranging insize from about 40 nm to 200 nm in the open form. In some embodiments,the process for producing the wsCNP having a molecule encapsulatedtherein can further include washing the precipitate with cold water.

In some embodiments, delivering to the subject can include intravenousinjection of the subject with the composition comprising the wsCNP. Insome embodiments, delivering to the subject can include inhalation ofthe composition comprising the wsCNP.

In some embodiments, the molecule encapsulated within the wsCNP can bean imaging agent and/or a therapeutic agent. In some embodiments, themolecule encapsulated within the wsCNP can be a therapeutic agent fortreatment of cancer and/or a brain disorder. In some embodiments, thebrain disorder can comprise dementia, vascular dementia, and/orAlzheimer's disease.

In some embodiments, the molecule encapsulated within the wsCNP can beone or a combination of Donepezil, TPP, a protein, a peptide, a smallmolecule, a nucleic acid, a single strand DNA, a double strand DNA, anRNA, an siRNA, an oligonucleotide, a gene, a gene fragment, an imagingagent, or a lanthanide.

In some embodiments, the molecule encapsulated within the wsCNP can befor delivery in a subject across the blood brain barrier (BBB).

In some embodiments, the wsCNP having a molecule encapsulated thereincan further include one or more biomolecules or divalent metals totarget delivery of the wsCNP with the encapsulated molecule to a cell,tissue, brain, or organ. In some embodiments, the biomolecule can be aprotein, a receptor, an aptamer, a ligand, or an antibody. In someembodiments, the divalent metal can be manganese. In some embodiments,the cell can be a cancer cell.

EXAMPLES

The following Examples have been included to provide guidance to one ofordinary skill in the art for practicing representative embodiments ofthe presently disclosed subject matter. In light of the presentdisclosure and the general level of skill in the art, those of skill canappreciate that the following Examples are intended to be exemplary onlyand that numerous changes, modifications, and alterations can beemployed without departing from the scope of the presently disclosedsubject matter.

Example 1 Preparation of Graphene Oxide Nanoparticles (GO)

The presently disclosed subject matter includes an eco-friendly methodof producing graphene oxide (GO) nanoparticles from wood charcoal or lowgrade coal, where the graphene sheets have an open size range of about40-200 nm. Wood charcoal or low grade coal in powdered form wasrepeatedly washed with toluene and/or acetone using a Soxhlet extractor,followed by washing with dilute hydrochloric acid, rinsing with water,and drying in air to reduce/eliminate aromatic hydrocarbons and otherassociated soluble organic compounds. The dried black powder was treatedin 10% sodium hydroxide solution and stirred magnetically at 40° C. toproduce a yellow-brown colored solution. The solution was separated andneutralized with dilute hydrochloric acid at pH of about 7. Uponstanding, a yellow-brown flaky precipitate appeared. The precipitate wasseparated by centrifugation, washed with cold water to free it fromchloride, and on dried in air. A red-brown solid with yield ranging from8 to 12% (based on the source material used) was produced.

The material was analyzed using spectroscopy, microscopy, and XRD, whichshowed the GO to have a size ranging from 40 nm to 200 nm as observed byDLS, AFM, and SEM study. FIG. 1A shows a size distribution of GOdetermined using DLS. In addition, the analysis revealed that the GOproduced by this method was freely soluble in alcohol and in water aboveneutral pH, and somewhat less soluble in the aqueous-acidic pH range.Upon aging overnight, in acidic pH 6.8), or after drying under vacuum,the structure of the GO was observed to change from oblique arches likea palm of a hand to a clenched first (a closed sphere). The clenchedfirst reverts back to the open first form at physiological pH of 7.4.FIG. 2B shows an electronic spectra of GO (solid line for freshlyprepared GO; dotted line for aged GO). FIG. 3C shows an electronicspectrum of the GO in PBS buffer pH 6.8 (solid line) and PBS buffer pH7.4 (dotted line). At pH 6.8, the absorption at 260 nm shows adistinctive peak, but at pH 7.4 the contour of the peak appears as ashoulder. The changes to the absorption features are similar to thoseobserved with the aged sample in alcohol. The spectra cross points whenthe GO was present at pH 6.8 versus when it was present at pH 7.4. Thedistinct change in the electronic spectra could be used as the marker toidentify the two structural forms, namely the open-fist (basic pH) andclenched-first (spherical, acidic pH) forms.

FIG. 2A is an Atomic Force Microscopy (AFM) image of open fisted GO.FIG. 2B is an AFM image of aged close fisted GO. FIG. 2C is a ScanningElectronic Microscopy (SEM) image of GO open first form upon exposurewith ammonia vapor. FIG. 2C is a SEM image of close fisted GO. FIG. 2Eis a High Resolution Transmission Electron Microscopy (HRTEM) image ofopen first GO. FIG. 2F is an HRTEM image of closed first GO.

Without being limited to any specific mechanism of action, thehypothesis that the GO nanoparticles were converting between the closedand open forms as a result of an epoxide-diol inter-conversion wastested. The closed GO is roughly spherical and can be expected to bethermodynamically more stable than the open first form. It is believedthat several adjacent phenolic hydroxyl groups on the surface of the GOparticipate in epoxide formation, resulting in the creation of anoblique arch like a palm of a hand that can close to a spherical form.The hypothesis was tested by the deuterolysis of the GO in closed firstform. Specifically, the GO was treated with ND₄OD-HD₂O and dried undervacuum at −37° C.

FIG. 3A shows the FTIR spectra of the open fisted GO form aftertreatment in NH₄OH—H₂O and drying under vacuum at −37° C. The spectra inFIG. 3A shows an absence of epoxide vibration with the appearance of acommon v(OH) vibration for dial merged with the v(OH) vibration fromcarboxylic acid group. FIG. 3B shows the FTIR spectra for GO treatedwith dilute hydrochloric acid and evaporated under vacuum. FIG. 3C showsthe FTIR spectra GO treated with ND₄OD—D₂O and dried under vacuum at−37° C. FIG. 3C shows the appearance of v(OD) around 2600 cm⁻¹ and showsthe disappearance of a peak around 1000 cm⁻¹, responsible for theepoxide vibration (C—O—C) [6]. When GO was treated with dilutehydrochloric acid and evaporated under vacuum, a (C—O—C) vibrationaround 1000 cm⁻¹ (FIG. 3B) was observed, which is not apparent in thespectra of FIG. 3A or 3C. In FIG. 3A, an epoxide vibration was notobserved, but there was a vOH at 3500 cm⁻¹, indicating an open fistedform of the GO under basic (NH₄OH—H₂O) conditions. FIG. 3B shows anepoxide vibration (C—O—C) around 1000 cm⁻¹ and the presence of vOH at3500 cm⁻¹. In FIG. 3C, the spectra confirm the epoxide-diolinter-conversion (presence of epoxide vibration) and shows appearance ofvOD around 2600 cm⁻¹ and the disappearance of a peak around 1000 cm⁻¹,confirming the open first form of GO in the N D₄OD-D₂O. The addition ofNID₄OD—D₂O opens the GO closed first form, which is shown in the FTIRspectra of FIG. 3C.

Without desiring to be limited to any particular mechanism of action, itis believed that the π-π stacking in the honeycomb hexagon structure ofcarbon in graphene is counteracted with the introduction of severaloxo-functional groups on the surface of GO. In the case of graphenequantum dots (see, e.g., U.S. Pat. No. 8,357,507), the size is limitedto within 20 nm; such a small unit with non-planar structure may not beexpected to have enough surface area for an energy stabilized sphericalshape. In contrast, a larger surface graphene oxide area (such as the GOresulting from the method provided herein in Example 1) would beexpected to respond to energy savings and result in a more stableclenched first (spherical) form. A size range of 40 nm to 200 nm withmaximum distribution in the range of 60-140 nm was determined for theopen form of the GO using DLS analysis (see FIG. 1A). The length andbreadth of the open form of the GO was also measured by AFM (see FIG.4A-4B). These data were used to calculate the expected size of theclosed GO sphere structure formed by either two open first sheets (twosuperficial halves) combining at the edges to form a spherical shape orby closure of a single sheet. The AFM data are shown in the histogramsize distribution graphs of FIG. 4. Particularly, FIG. 4A illustratesthe size distribution of GO in the open first structure. FIG. 4Billustrates the size distribution of GO in the closed fist, sphericalstructure. The range of size distribution observed for the open andclosed first forms of GO using AFM indicates the possibility of either asingle sheet closure or closure of two or more sheets, and the closedspherical form is energetically favored.

Experimental Methods: Electronic spectral measurements were carried outwith JASCO, V-630 spectrophotometer and fluorescence spectra wererecorded with Photon Technology International (PTI) QuantaMaster™ 300.For Scanning Electron Microscopy (SEM), a SUPRA 40VP field-emission SEM(Carl Zeiss NTS GmbH, Oberkochen, Germany) equipped with anenergy-dispersive X-ray (EDX) unit, in high vacuum mode operated at 10kV was used for the visualization of the size and morphology of GO andGO-TPP. The powder X-ray diffraction data was collected on a Bruker 08Advance X-ray diffractometer using Cu Ka radiation (Δ=1.5418 Å)generated at 40 kV and 40 mA. Five mg of GO sample was dissolved in 100mL ethanol to determine the particle size using dynamic light scattering(DLS), nanotrac wave, model, W3222. TEM and images were taken on FEI,TECHNAI-T-20 machine operated on the voltage 200 kV.

Example 2

Methods for Encapsulation and Release of Molecules within Water SolubleCarbon

Nanoparticles (wsCNPs) Based on the observation of the reversiblestructural change between the open and closed spherical forms of the GOresulting from pH variation, the ability of the GO to be loaded with andrelease a molecule was investigated. For these studies, the moleculestetraphenylporphyrin (TPP) and donepezil were selected. Both moleculesare spectrally identifiable, and TPP is considered to be a largemolecule for a therapeutic. TPP is also considered a model for severalporphyrins in photodynamic therapy [7]. Donepezil is anacetylcholinesterase inhibitor for the treatment of Alzheimer's diseaseknown chemically as(±)-2,3-dihydro-5,6-dimethoxy2-[[1-(phenylmethyl)-4-piperidinyl]methyl]-1H-inden-1-one hydrochloride and has an empirical formula ofC₂₄H₂₉NO₃ and a molecular weight of 415.96. It is a white crystallinepowder and is freely soluble in water, chloroform, and DCM, slightlysoluble in ethanol and acetonitrile, and practically insoluble inn-hexane.

Encapsulation of the each of the molecules within the GO was performedas described. 2 mg donepezil (AdooQ BioScience, Irvine, Calif.) wasdissolved in 6 mL water and 5 mg freshly prepared GO was separatelydissolved in 5 mL ethanol. The two were mixed, left at room temperaturefor 4 hours, and the mixture was evaporated to dryness under vacuum at−37° C. The mass was washed repeatedly with water containing very dilutehydrochloric acid and then extracted with alcohol and evaporated todryness under vacuum at −37° C., resulting in a “GO-donepezil”composite.

A similar method was followed to encapsulate TPP within the GO, bymixing a solution of TPP in toluene with a solution of freshly preparedGO dissolved in ethanol. The mixture was evaporated to dryness undervacuum at −37° C., resulting in a brown solid. The solid was washedseveral times with toluene under sonication. In this manner, essentiallyall the TPP not encapsulated within the GO was removed resulting in a“GO-TPP” composite.

The composites were subjected to various spectroscopic and microscopicinvestigations, shown in FIG. 5A-5H. Electronic spectral measurementsand microscopic analyses were carried out according to the experimentalmethods described in Example 1 above. Both TPP and donepezil areinsoluble in water. FIG. 5A is an HRTEM image of the GO-TTP compositeprepared as described above and after treatment with NH3 to increase thepH, showing the GO in the open form. FIG. 5B is an HRTEM image of theGO-TPP prepared as described above, showing the GO in the closed form,and an inset of an enlarged section of the composite that shows thepresence of stacked TPP within the GO. FIG. 5C is an SEM image of theGO-TPP composite after treatment with NH₃ to increase the pH, showingthe GO in the open form. FIG. 5D is an SEM image of the GO-TPP compositeprepared as described above, showing the GO in the closed form. FIG. 5Eis an electronic spectrum of GO-TPP composite prepared as describedabove in PBS buffer pH 7.4, showing the open form of the GO allowing forrelease of TPP (inset: electronic spectrum of dichloromethane extract ofthe GO-TPP buffer showing the features of TPP). FIG. 5F is an electronicspectrum of the GO-TPP prepared as described above in PBS buffer pH 6.8,showing features of the encapsulated TPP within the closed form (TPP wasnot detected after dichloromethane extraction of the GO-TPP buffer).FIG. 5G is an electronic spectrum of the GO-donepezil composite preparedas described above in PBS buffer pH 7.4, showing the open form of GOallowing for release of the donepezil (inset: electronic spectrum ofdichloromethane extract of the GO-donepezil buffer showing the featuresof donepezil). FIG. 5H is an electronic spectrum of the GO-donepezilcomposite prepared as described above in PBS buffer pH 6.8, showingfeatures of the encapsulated donepezil within the closed form of the GO(donepezil was not detected after dichloromethane extraction of theGO-donepezil buffer).

Powder X-ray diffraction (XRD) was also performed on the GO-TPPcomposite prepared according to Example 1 above. FIG. 6A is an XRDspectrum of GO prepared as described above without encapsulated TPP.FIG. 6B is an XRD spectrum of GO-TPP composite prepared as describedabove, showing sharp peaks for TTP along with the broad peaks of the GO.FIG. 6C is an enlarged view of the spectrum from FIG. 6B to more clearlyillustrate the presence of both the broad peaks from the GO and thesharp peaks from the TPP.

The following experiments were performed to investigate whether othergraphene based water soluble carbon nanoparticles (wsCNPs) (produced bymethods other than those described herein) can change from an open firsttype of structure at basic pH to a closed, spherical structure at pH ofabout 6.8 and below. The tests were performed using water solublequantum carbon dots (wsCdot) described in U.S. Pat. No. 8,357,507. Asdescribed in the '507 patent, wsCdot have a size range of about 2-20 nmin diameter. The wsCdot particles were prepared according to the methodsdescribed in the '507 patent and investigated using microscopic andelectronic spectral measurements as described herein above for the GO.FIG. 7A shows aged wsCdot and FIG. 7B shows aged wsCdot after exposureto NH₃ vapor. The figures illustrate a change from a spherical structureto a flat open structure after the NH₃ treatment.

Donepezil dissolved in water and wsCdot separately dissolved in ethanolwere mixed in a 1:10 weight ratio. The mixture was made basic at pH 8 byaddition of dilute NaOH. After a few minutes, the mixture was acidifiedwith dilute HCl to a pH around 6, and the mixture was evaporated todryness under vacuum at −37° C. The mass was extracted with alcohol andevaporated to dryness under vacuum at −37° C., resulting in a“wsCdot-donepezil” composite. FIG. 7C illustrates electronic spectra ofthe wsCdot-donepezil composite in PBS, pH 6.8, where extraction with DCMdid not remove the donepezil from the composite. FIG. 7D illustrateselectronic spectra of the wsCdot-donepezil composite in PBS, pH 7.4,where extraction with DCM revealed a signature donepezil spectrum (shownin the inset).

Freshly prepared wsCdot in the open structure was loaded by dissolvingin either water or ethanol and mixing with donepezil in water. Themixture was evaporated to dryness under vacuum at −37° C. The resultingwsCdot-donepezil composite was shown to contain encapsulated donepezilusing electronic spectral analysis.

DNA was encapsulated inside the wsCNP prepared according to the methoddescribed in Example 1. Particularly, calf thymus DNA (Sigma Aldrich)was mixed with an aqueous alcoholic solution of wsCNP and the resultantclear solution was vacuum dried at −37° C. The mass was washed with coldwater to remove free DNA not encapsulated within the wsCNP to produce aGO-DNA composite. Electronic spectra were compared in phosphate bufferedsaline at pH 6.5 for DNA alone, GO alone and the GO-DNA compositedissolved in the buffer. The results are shown in FIG. 8A-8C.Particularly, FIG. 8A is the electronic spectra for the calf thymus DNAalone, showing a peak at 259 nm. FIG. 8B is the electronic spectra forthe GO alone. FIG. 8C is the electronic spectra for the GO-DNAcomposite, showing the characteristic absorption peak of DNA at 259 nmand also showing the background absorption of the GO. The electronicspectrum for the GO-DNA composite was taken immediately after thedissolution of the composite the in the buffer, demonstrating thatfragments of DNA or other types of nucleic acid molecules (such as thoseencoding a gene of interest or a siRNA, for example) can be encapsulatedin the wsCNP.

A wsCNP can be encapsulated with any of the lanthanides. Lanthanides areuseful as imaging agents and sensors. For the encapsulation, one or morelanthanides was mixed with an aqueous or alcoholic solution of wsCNP inthe open form and the resultant solution was vacuum dried at −37° C. Themass was washed with cold water to remove free lanthanide notencapsulated within the wsCNP to produce a GO-lanthanide composite.

Example 3

wsCNP Crosses Blood Brain Barrier in Transgenic Mouse

An experiment was performed to investigate whether wsCNP are able tocross the blood brain barrier (BBB). In the experiment, wsCNP producedaccording to the methods described in the '507 patent was injected intothe tail of transgenic mice. The transgenic mice had pericytedysfunction, associated with neurodegenerative diseases. Pericytefunction is an important component of the neurovascular unit thatcontributes to the integrity of the BBB. BBB disruption or disintegrityin the affected the brain can allow for passive diffusion. Byintravenous administration of the wsCNP to a mouse, it was demonstratedthat the fluorescent wsCNP smoothly crossed the BBB into the brain oftransgenic FVBN mice.

Cerebral autosomal dominant arteriopathy with subcortical infarcts andleukoencephalopathy (CADASIL), one of the most common small vesseldiseases, is a major contributor of vascular dementia in humans.Primarily, it is known to be caused by Notch3 mutation. Recently,ultra-structural changes in pericytes have been shown in CADASIL.

Therefore, BBB integrity was assessed in a murine model of CADASIL(R169C; Tg88 by overexpression of mutated transgene) using wsCNP. Theinherent properties of wsCNP make it ideal for delivery of therapeuticand/or imaging agents. For example, properties including low toxicity,amphipathic properties allowing for permeability, fluorescence in theblue, green, and red spectrums, and suitable dimensions and propertiesfor loading and release of imaging and/or therapeutic molecules. Theproperties of the wsCNP include permeability through blood vessels,allowing for passage through hydrophilic as well as lipophilic routeseven without pegylation.

Using intra-arterial injection of wsCNP, the brain of a mouse was imagedin-vivo in real time by constant monitoring for at least 30 minutesafter injection of the wsCNP. The elasticity of the blood vessel and thegradual enhancement in florescence due to the wsCNP clearly demonstratedthe passage of the wsCNO along the blood vessel and into the brain (datanot shown). The mouse was then sacrificed and a brain slice was imagedby fluorescence microscopy using two color channels to demonstrate thepresence of wsCNP in the brain cortex (the brain vessels were labeledwith lectin by intravenous injection to demarcate the fluorescence dueto wsCNP in brain vessels of the cortex (data not shown)). It was notedthat such easy passage of wsCNP across BBB into the brain may not takeplace in healthy mice, suggesting the utility of this process fortreatment of brain disorders involving vascular degeneration. It wasinferred that the passage of wsCNP across the BBB was only facilitatedin the case of the noted vascular defect.

In addition, adult C57B6 mice (6 months old) were injected into thebrain with a small number of mouse GBM cells (“orthotopic allograft”).After tumor establishment (two weeks), small amounts of GFP+ cells wereintroduced into the mouse brain. The mice were then injected into theblood stream via the tail vein with wsCNP (concentration 1 mg/mL inwater, 10 μL per gm body weight of each of the mice) and 3 separate timeperiod exposures were recorded (4, 12, and 24 hours). The brain wasfixed, cut, and imaged as single slice under confocal microscope andimaged. FIG. 9 illustrates images of the GFP+ cells (tumor cells), bloodvessels, and the wsCNP as indicated with arrows. The image shows theability of the wsCNP to cross the BBB.

Experimental Section: The wsCNP was synthesised as reported. A 1.0 mg/mLconcentration of wsCNO was made and 10.0 μL per gm of the body weight ofmice was administered by intravenous tail vein injection with a dose of200 μL for 20 g mice or 250 μL for 25 g mice. Six to 8-month oldtransgenic FVBN mice were used (R169C; Tg88 by over expression ofmutated transgene that were 23 to 26 g) obtained from either CharlesRiver (Kisslegg, Germany) or Jackson Laboratories (Bicester, UK). Theanimals had free access to tap water and pellet food. Mice within oneexperiment were housed individually throughout the experiment. Allanimal experiments were conducted in accordance with institutionalguidelines and approved by the government of Upper Bavaria. Animals wereanesthetized by an intra-peritoneal injection of medetomidine (0.5mg/kg, DOMITOR), fentanyl (0.05 mg/kg), and midazolam (5 mg/kg,DORMICUM). Following induction, the mice were endotracheally intubatedand ventilated using a volume-controlled ventilator. Body temperaturewas maintained at 37±0.1° C. with a feedback-controlled heating pad.Body temperature and end-tidal CO₂ were monitored continuously.Subsequently, the animals were immobilized in a stereotactic frame, andone square (2 mm×2 mm) cranial window was prepared over thefronto-parietal cortex of the right hemisphere. The window was preparedunder continuous cooling with saline, the dura mater was carefullyremoved, and a custom-made cover glass (Schott Displayglas, Jena,Germany) was inserted and affixed with dental cement (Cyano Veneer,Hager & Werken, Duisburg, Germany). For maintenance of physiologicalconditions, the exposed dura mater was continuously irrigated with warmisotonic saline solution (0.9% NaCl at 37° C.). The cerebral microvessels were then investigated in this area. The animals were placed ona computer-controlled microscope stage for repeated analyses of the samevessels. Visualization of the microvessel was performed using an uprightepifluorescence microscope AxioscopeVario (Zeiss) with COLIBRI fordetection of fluorescent wsCNO in FITC channel. The vessels werevisualized with a saltwater immersion objective.

After two baseline recordings of selected cerebral arterioles andvenules in the window, the animals were injected with wsCNP (n=4 miceper group) by tail vein injection both in transgenic and control mice.The previously observed vessels were constantly being monitored up to 30min after injection. At the end of each experiment, the animals weresacrificed by transcardiac perfusion with 4% PFA. Image and videoacquisition were done using a Zeiss AxioCam MRm monochrome cameraequipped with the microscope and COLIBRI illumination system. The systemwas controlled with the Zeiss AxioVision software tools. The videoacquisition was made using Fast acquisition sub tool in themultidimensional imaging tool of the software in the FITC channel.

Adult C57B6 mice (6 months old) were injected into the brain with asmall number of mouse GBM cells (“orthotopic allograft”). After tumorestablishment (two weeks), small amounts of GFP+ cells were introducedinto the mouse brain. The wsCNP (concentration 1 mg/mL in water), 10 μLper gm body weight of each of the mice with 3 time periodexposure—4-12-24 hours were injected into the blood stream via the tailvein. The brain was fixed, cut, and imaged as single slice underconfocal microscope and imaged where color distinction in tumor GFP+cells were green, wsCNO was red, vacuolar marker antibody was blue andblood channel was white (images are shown herein in black and white).

Example 4

Water Soluble CNP Containing Bivalent Metal for Targeted Delivery to theBrain

In these experiments, manganese (Mn) or another divalent metal wasincorporated into the wsCNP to allow for targeting of the wsCNP to thebrain. In this manner, the wsCNP was shown to utilize the capacity of Mnto be taken up by nerve terminals via the bivalent metal transporter ofthe olfactory nerves where it can be further transported to the entirebrain. Thus, wsCNP can be loaded with a therapeutic agent and/or animaging agent and also contain incorporated divalent metal to advantageof the metal transporter to target delivery of the wsCNP contents to thebrain of a subject.

Manganese acetylacetonate (Mn(acac)₃) was incorporated into the GOproduced according to the method in Example i by mixing the GO andMn(acac)₃ in ethanol. The solution was vacuum dried at −37° C.,resulting in a solid powder form. The powdered mass was washed withdistilled water to remove any excess Mn(acac)₃. FIG. 10A-10D showelectronic spectra of the: (A) Untreated GO in ethanol; (B) Mn(acac)₃ inethanol; (C) GO containing Mn(acac)₃; and (D) Simulated spectra ofcombined GO and Mn(acac)₃. The spectral data show that the Mn remainsassociated with the GO at the pH 6.5. The experiment shows that abivalent metal (such as Mn) can be incorporated into the wsCNP to takeadvantage of the metal transporter to target delivery of the wsCNP tothe brain.

In another experiment, manganese acetylacetonate (Mn(acac)₃) wasincorporated into a wsCNP and a therapeutic agent and/or imaging agentwas encapsulated within the wsCNP according to the following procedure.A Mn salt and a therapeutic agent and/or imaging agent for encapsulationare added together in a solution (or two solvents were mixed where boththe therapeutic agent and/or imaging agent and the Mn salt were soluble,for example, manganese acetate in alcohol and the therapeutic agent indichloromethane). In one example, the imaging agent was any of thelanthanides. The ratio of the therapeutic agent and/or imaging agent andMn can vary depending on the required concentration of each. To theabove solution, wsCNP in open form in aqueous or alcoholic solution wasadded. The solution was vacuum dried at −37° C., resulting in a solidpowder form that has the incorporated Mn and encapsulated therapeuticagent and/or imaging molecule. The powdered mass was washed withdistilled water to remove any excess Mn salt and was then washed with asolvent (such as, for example, dichloromethane) to remove therapeuticagent that was not encapsulated. The washed powdered form (free fromexcess Mn salt and therapeutic agent/imaging agent) has potential foradministration by nasal insufflation. This experiment is an exampleshowing that a bivalent metal such as Mn can be incorporated into thewsCNP to take advantage of the metal transporter to target delivery ofthe wsCNP (and its contents such as a therapeutic agent and/or animaging molecule) to the brain as nasal insufflations.

Any patents or publications mentioned in this specification areindicative of the levels of those skilled in the art to which thepresent disclosure pertains. These patents and publications are hereinincorporated by reference in their entirety to the same extent as ifeach individual publication was specifically and individually indicatedto be incorporated by reference. One skilled in the art will readilyappreciate that the present disclosure is well adapted to carry out theobjects and obtain the ends and advantages mentioned, as well as thoseinherent therein. The present Examples along with the methods describedherein are presently representative of preferred embodiments, areexemplary, and are not intended as limitations on the scope of theinvention. Changes therein and other uses will occur to those skilled inthe art which are encompassed within the spirit of the presentdisclosure as defined by the scope of the claims.

Example 5

Cdot or GO Nanoparticles Reach Neurons of Healthy or Tumor-Infected MicecDot Brain Distribution in a Glioblastoma Mouse Model Glioblastoma isthe most devastating form of brain cancer with a median survival of 15months. The only FDA-approved therapy after tumor resection (treatmentwith radiation concomitant with the chemotherapeutic temozolomide)invariably fails. Most FDA-approved drugs to treat cancer do not passthe blood-brain barrier, thus cannot be tested as experimental drug forglioblastoma. Nanoparticles are a promising tool for drug delivery buthas not been adapted to be utilized for neurological disease yet. Theexample below tests whether cDots could pass the blood brain barrier asthe first step to design a novel drug delivery system to the deep braintissue.

Mouse glioblastoma cells (10,000) were orthotopically injected in themid-brain (diencephalon) of anesthetized wildtype mice (strain C57B6)under aseptic conditions. The mice were kept in their home cage for 2weeks to allow glioblastoma growth and incorporation into thesurrounding brain tissue. cDots were resuspended at 1 mg/mL and 3 mg/mLin sterile saline, and 100 μL per mouse were injected into the tailvein. 6, 12, or 24 hours after cDot injection, mice were deeplyanesthetized and intra-cardial perfused with fixative (4%para-formaldehyde). cDots did not display overt toxicity since mice wereasymptomatic during the period of the experiment and the liver appearednormal. Brains were subsequently cut into 50 μm sagittal sections, andsections with GFP-expressing tumor mass were selected forimmunofluorescence staining. cDots were found distributed throughout thetumor mass, both co-localizing with blood vessels and the surroundingtissue, indicating that cDots had left the vascular system and diffusedinto the surrounding brain tissue. cDots were also found throughoutnormal brain tissue, both in proximity and far distant from the tumormass, demonstrating the general ability of cDots to penetrate the bloodbrain barrier. We did not find a difference in cDots density in normalbrain tissue when comparing 6 and 24 hrs time points, and low and highcDot injection concentrations, suggesting that cDots reach their maximaltissue concentration within 6 hrs, which cannot be further increased byincreased cDot plasma levels. The cDot density in normal brain tissuewas higher than inside the tumor mass, which may be due to the poorvascularization of tumors or reduced diffusion rates into the tumor(e.g., caused by free carboxy groups on the surface of the cDots and anacidic tumor microenvironment).

The cell types cDots were targeting in the brain were then identified.In the normal cerebral cortex, the majority of cDots were found closelyassociated with NeuN⁺ pyramidal neurons. It appeared that cDots alsohave the ability to enter the cytoplasm of neurons. Similarly, neuronsin proximity of the tumor mass were decorated with cDots. Some tumorcells were decorated with cDots or appeared to have incorporated cDots.In contrast, there was no evidence that cDots associated with healthyastroglial cells (the likely cell of origin for glioblastomas) in thecerebral cortex. Microglia (part of the immune response in brain tissue)phagocytized cDots both in normal brain tissue and in the tumor mass.cDots decorated neurons and microglial at comparable rates.

Thus, in summary, cDots were injected in the bloodstream of a mousemodel for glioblastoma, the most devastating form of brain cancer. Micewere sacrificed after 6-24 hrs and brain distribution of cDots wasassessed by confocal microscopy of fixed brain sections. cDots readilypassed the blood brain barrier and were distributed throughout normaland tumor tissue. Cellular analysis revealed that cDots were primarilyassociated with neurons but not with glial cells, and that the cDotdensity was lower inside the glioblastoma compared to normal braintissue.

Excreta samples were taken every 24 hours from a mouse that was injectedwith cDot or GO nanoparticles via the tail vein. Samples were collectedon cotton swabs, processed, and analyzed under a fluorescent microscopein the red color range. Though the nanoparticles fluoresce in blue(around 475 nm), green (around 510 nm), and red (around 650 nm) regionsof the spectrum, for this study the focus was on the red region ascommon bio molecules available naturally do not fluoresce in thisregion.

The intensity of the fluorescence is related to cDot or GO. Accordingly,the length of time it took the nanoparticles to excrete was studied. Theintensity of the fluorescence was low for day 1 and it steadilyincreased to suggest the rate of excretion increased on day 2 withhighest intensity observed at day 3. The intensity started to decreasefrom day 4 and was not visible after day 5, indicating the nanoparticleswere excreted from the system after 5 days, as shown in FIG. 11 (showingfluorescence intensity (a.u.) versus time (days). The cDot or GOnanoparticles are nontoxic (soluble and readily excreted from the body)and the LD50 of GO or cDot was found to be 1098 mg/kg body weight.

FIG. 12A-12D indicate fluorescent microscope images (4-hour post cDot orGO injection) for normal mice and FIG. 12E-121 indicate fluorescentmicroscope images (4-hour post cDot or GO injection) for tumor-infectedmice. FIGS. 12A and 12E show blood vessels. FIGS. 12B and 12G show cDotand GO as dots. FIG. 12F shows tumor cells conjugated or tagged withGFP. Neurons are shown in FIGS. 12C and 12H. Brain tissue in normal micein merged image (FIG. 12D) show C/G as dots present near neuron cells.

It can therefore be determined that cDots may be a promising carrier fortargeting drugs to neurons throughout the brain. To a lesser extent,cDots could be used for glioblastoma treatment. The incorporation ofmolecular targeting ability into the cDot surface may be necessary forincreased cell type or tumor selectivity.

Materials and Methods

Mice. C57B6 mice (“Black 6 mice”) were orthotopically injected into thediencephalon (located central inside the brain) with GFP-tagged mouseglioblastoma cells. On day 14, after a glioblastoma had formed, 100 μLof cDots suspended in sterile saline was injected into the tail vein at1 mg/mL and 3 mg/mL concentration. After 6,12, or 24 hrs mice weredeeply anesthetized and fixed by intra-cardial infusion of 4%paraformaldehyde. All procedures had been approved by the UNCInstitutional Animal Use and Care Committee.

Tissue processing and imaging. Brains were sagittally cut into 50 μmstick section with a Leica vibratome, followed by processing forimmunofluorescence staining. Primary antibodies were used as molecularmarkers to identify neurons (NeuN), astroglia (BLBP), microglia (Iba1)or endothelial cells enclosing blood vessels (CD31). The molecularmarkers were detected by CF405 or CF647 fluorescent dye-conjugatedsecondary antibodies. Cell nuclei were counterstained with DAPI. Mountedbrain sections were imaged with a ZEISS LSM780 confocal microscope. GFPwas detected on the green channel (excitation 488 nm, emission band500-550 nm), cDots on the red channel (excitation 561 nm, emission band570-630 nm), DAPI and CF405 dyes on the blue channel (excitation 405 nm,emission band 420-470 nm), and CF647 dyes on the far-red channel(excitation 647 nm, emission band 650-720 nm). Images were exported asTIF files with Zeiss ZEN 2012 software.

REFERENCES

-   1. Hummers W S, Otteman R E, “Preparation of Graphitic Oxide,” J.    Am. Chem. Soc. 1958, 80: 1339-1339.-   2. Boehm H P, Scholz W. “Der” Verpuffungspunkt” des    Graphitoxids,” Z. Anorg. Allg. Chemie 1965, 335: 74-79.-   3. Marcano D C, Kosynkin D V, Berlin J M, Sinitskii A, Sun Z,    Slesarev A, et al. “Improved Synthesis of Graphene Oxide,” ACS Nano    2010, 4: 4806-4814.-   4. Ye R, Xiang C, Lin J, Peng Z, Huang K, Yan Z, et al., “Coal as an    abundant source of graphene quantum dots,” Nat. Commun. 2013, 4.-   5. Ministry of Coal, Government of India, “Coal Grades,” 2014 24    Sep. 2014 [citedl5 23 Apr. 2015] Available from: http://www.coal.    nic. in/contenVcoal-grades-   6. Guerrero-Contreras J, Caballero-Briones F, “Graphene oxide    powders with different oxidation degree, prepared by synthesis    variations of the Hummers method,” Mater. Chem. Phys. 2015, 153:    209-220.-   7. Ethirajan M, Chen Y, Joshi P, Pandey R K, “The role of porphyrin    chemistry in tumor imaging and photodynamic therapy,” Chem. Soc.    Rev. 2011, 40: 340-362.-   8. Tsuda A, Nagamine Y, Watanabe R, Nagatani Y, Ishii N, Aida T,    “Spectroscopic visualization of sound-induced liquid vibrations    using a supramolecular nanofiber,” Nat. Chem. 2010, 2: 977-983.-   9. Shen H, Zhang L, Liu M, Zhang Z, “Biomedical Applications of    Graphene,” Theranostics 2012, 2: 283-294.-   10. Heydorn W E, “Donepezil (DZ): a new acetylcholinesterase    inhibitor. Review of its pharmacology, pharmacokinetics, and utility    in the treatment of Alzheimer's disease,” Exp. Opin Invest. Drugs    1997, 6: 1527-1535.

What is claimed is:
 1. A composition comprising graphene oxidenanoparticles (GO) comprising a plurality of graphene sheets having aplurality of carboxylic and hydroxyl groups and interconvertible openand closed forms; the open form having a size of about 40 nm to 200 nm;the closed form having a diameter of about 2 nm to 120 nm; where theopen form can be converted to the closed form at a pH of about 6.8 orlower; and the closed form can be converted to the open form at a pH ofabout 7.2 or higher.
 2. The composition of claim 1, wherein thecarboxylic groups comprise at least about 20% of the total weight of theGO.
 3. The composition of claim 1, wherein the GO has a solubility inaqueous solution at a concentration of about 1 mg GO/mL.
 4. Thecomposition of claim 1, wherein the GO displays fluorescence in theblue, green, red, and infrared spectra.
 5. The composition of claim 1,wherein the GO has amphiphilic properties.
 6. A method for reversibleencapsulation of a molecule within the GO of claim 1, the methodcomprising: contacting the open form GO with a molecule to beencapsulated; converting the open form GO to the closed form GO with themolecule encapsulated therein by adjusting the pH to about 6.8 or lower;and the molecule is be released from the closed form GO at a pH of about7.2 or higher.
 7. The method of claim 6, wherein the molecule is one ormore of donepezil, tetraphenylporphyrin, a protein, a peptide, a smallmolecule, a nucleic acid, a single strand DNA, a double strand DNA, anRNA, an siRNA, an oligonucleotide, a gene, a gene fragment, an imagingagent, a lanthanide, or a combination thereof.
 8. A compositioncomprising a water-soluble carbon nanoparticle (wsCNP) having anencapsulated molecule therein, the wsCNP comprising a plurality ofgraphene sheets having a plurality of carboxylic and hydroxyl groups andinterconvertible open and closed forms; the open form having a size ofabout 40 nm to 200 nm; the closed form having a diameter of about 2 nmto 120 nm; where the open form can be converted to the closed form at apH of about 6.8 or lower; and the closed form can be converted to theopen form at a pH of about 7.2 or higher.
 9. The composition of claim 8,wherein the encapsulated molecule is an imaging agent or a therapeuticagent.
 10. The composition of claim 8, wherein the encapsulated moleculeis a therapeutic agent for the treatment of a brain disorder.
 11. Thecomposition of claim 8, wherein the encapsulated molecule is one or moreof donepezil, tetraphenylporphyrin, a protein, a peptide, a smallmolecule, a nucleic acid, a single strand DNA, a double strand DNA, anRNA, an siRNA, an oligonucleotide, a gene, a gene fragment, an imagingagent, a lanthanide, or a combination thereof.
 12. The composition ofclaim 8, wherein the encapsulated molecule is donepezil ortetraphenylporphyrin.
 13. The composition of claim 8, wherein theencapsulated molecule is a therapeutic agent for treatment of cancer.14. The composition of claim 8, further comprising one or morebiomolecules or divalent metals for targeted delivery of the wsCNP withthe encapsulated molecule to a cell, tissue, brain, or organ.
 15. Thecomposition of claim 14, wherein the biomolecule is a protein, areceptor, an aptamer, a ligand, or an antibody; and the divalent metalis manganese (Mn).
 16. A method for delivering a water-soluble carbonnanoparticle (wsCNP) having an encapsulated molecule therein, the methodcomprising: delivering to a subject a water-soluble carbon nanoparticle(wsCNP) having a molecule encapsulated therein, where the wsCNPcomprises a plurality of graphene sheets having a plurality ofcarboxylic and hydroxyl groups and interconvertible open and closedforms; the open form having a size of about 40 nm to 200 nm; the closedform having a diameter of about 2 nm to 120 nm; where the open form canbe converted to the closed form at a pH of about 6.8 or lower; and theclosed form can be converted to the open form at a pH of about 7.2 orhigher; and the encapsulated molecule is released from the wsCNP at a pHof 7.4 after delivery.
 17. The method of claim 16, wherein deliveringcomprises intravenous injection or inhalation.
 18. The method of claim16, wherein the molecule is one or a combination of donepezil,tetraphenylporphyrin, a protein, a peptide, a small molecule, a nucleicacid, a single strand DNA, a double strand DNA, an RNA, an siRNA, anoligonucleotide, a gene, a gene fragment, an imaging agent, or alanthanide.
 19. The method of claim 16, wherein the molecule isdonepezil or tetraphenylporphyrin.
 20. The method of claim 16, whereinthe molecule is a therapeutic agent for the treatment of a braindisorder.
 21. The method of claim 20, wherein the brain disordercomprises dementia, vascular dementia, or Alzheimer's.
 22. The method ofclaim 21, wherein the molecule is a therapeutic agent for treatment ofcancer.
 23. The method of claim 16, wherein the molecule is deliveredacross the blood brain barrier (BBB).
 24. The method of claim 16,wherein the wsCNP further comprises one or more biomolecules or divalentmetals for targeted delivery of the wsCNP with the encapsulated moleculeto a cell, tissue, brain, or organ.
 25. The method of claim 24, whereinthe biomolecule is a protein, a receptor, an aptamer, a ligand, or anaptamer; and the divalent metal is manganese (Mn).
 26. The method ofclaim 18, wherein the wsCNP is produced by a process comprising: (a)treating a material comprising one or a combination of wood, charcoal,low grade coal, or carbonized plant biomass with a dilute alkalisolution to form a mixture of components including insoluble materialand a second solution; (b) separating the second solution from theinsoluble material; (c) neutralizing the second solution to form aprecipitate; and (d) separating the precipitate from the neutralizedsecond solution; wherein the precipitate comprises graphene oxidenanoparticles (GO) having a plurality of graphene sheets having aplurality of carboxylic and hydroxyl groups and interconvertible openand closed forms; the open form having a size of about 40 nm to 200 nm;the closed form having a diameter of about 2 nm to 120 nm; where theopen form can be converted to the closed form at a pH of about 6.8 orlower; and the closed form can be converted to the open form at a pH ofabout 7.2 or higher.